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Agree with the above, it's pretty easy to check and adjust the AFM.
What year is the car? Some components are different between early and late cars (AFM, DME, O2 sensor)...I am assuming it's a late car, based on the DME & water damage
Cap can look clean, but have a crack, as can the wires.
You ran it without the exhaust and still had the same problem?
The fact that it revs without issue when under no load still has me thinking it is somehow fuel related. There is a strainer in the gas tank, but I am not sure of anyone having issues with that getting so plugged it causes running problems. I would revisit the Pressure regulator, Spencer stated it should be at 30 PSI at idle and 37 at WOT. You got up to 33 PSI, but then dropped to 25 PSI - this could be an issue
I don't have experience with the speed and reference sensor issues that others have had, but know they can cause running issues.
Good point on the fuel pressure. It could be flagging under load. A flow test is a good indication as it is hard to rig up a pressure gauge you can read with the car under load. Jumper the DME relay and see how fast it'll fill up a 2 liter bottle, should be under 2 minutes. Do not try to crank the car for this, too many sparks!
Thank you guys so much for the information I think each one of you is a Porsche expert
The car is a 1986 model.
I'm going to try the flow test now.
And the ignition wires seem to be fine however the outer heat layer does seem to be cracking.
In addition I took the DME apart and cleaned it with electronics cleaner and the car ran noticably better. Could it be possible that the DME is damaged because of water.
So I did the soda bottle test at the fuel pressure test port and directly at the fuel feed line and both times it filled the 2 liter bottle up at around 2 minutes 30 seconds. Would this mean there is a fuel flow issue.
You guys are checking a lot of weird things that aren't going to change while a car sits parked. A timing belt is not going to move itself by a tooth. A spark plug wire is not going to plug itself into a different plug and if it magically did so, the car would shudder and shake so violently once started that you wouldn't mistake it for anything else.
As V2 says, that gas looks like crap. Worn out caps and rotors tend to make the cars hard to start when cold, but I've never noticed a difference in how well they run once started. I still think O2 and AFM, and if you already checked afm it's a hell of a lot easier to screw in a $35 O2 sensor (esp if it's overdue for replacement anyway) than monkey with timing belts, etc.
If there's still old gas in there (as opposed to your existing gas being fresh but mocha flavored), I'd replace it with fresh and a bottle of techron then continue with the other troubleshooting items. My 968 sat for over a year outside in Phoenix (dead water pump), when I finally got around to fixing it, it started up with the old gas (very rough!) then started to settle down the more it was driven and even passed emissions with the old gas still in it. It didn't start to feel "fast" again until a few miles after replacing O2 and TPS.
Good luck, it's a fun mystery watching you bring this car back to life.
sounds sufficient, probably worth checking the fuel filter if you havent already.
why is your gas the color of the coke that was in that bottle? lol
Haha, in the original post I made a typo, I said the car sat for 2 years but what I meant to say is that it sat for 7 years (at least that's what the seller told me). So I think because of this there's some kind of varnish in the gas tank that turns the gas yellow. I did replace the filter, and blow out the lines with air but now I'm thinking that more gunk has clogged the lines.
You guys are checking a lot of weird things that aren't going to change while a car sits parked. A timing belt is not going to move itself by a tooth. A spark plug wire is not going to plug itself into a different plug and if it magically did so, the car would shudder and shake so violently once started that you wouldn't mistake it for anything else.
As V2 says, that gas looks like crap. Worn out caps and rotors tend to make the cars hard to start when cold, but I've never noticed a difference in how well they run once started. I still think O2 and AFM, and if you already checked afm it's a hell of a lot easier to screw in a $35 O2 sensor (esp if it's overdue for replacement anyway) than monkey with timing belts, etc.
If there's still old gas in there (as opposed to your existing gas being fresh but mocha flavored), I'd replace it with fresh and a bottle of techron then continue with the other troubleshooting items. My 968 sat for over a year outside in Phoenix (dead water pump), when I finally got around to fixing it, it started up with the old gas (very rough!) then started to settle down the more it was driven and even passed emissions with the old gas still in it. It didn't start to feel "fast" again until a few miles after replacing O2 and TPS.
Good luck, it's a fun mystery watching you bring this car back to life.
cheers,
c
Thanks for the kind words, I did check the AFM resistance and did the test with the barn door opening and closing while checking it with the multi meter and it tested well. In addition I cleaned and then tested the throttle position sensor, and it also tested well. The O2 sensor however I have not checked or replaced yet. And you bring up a very good point with the O2 because when I took off the exhaust to test it it ran noticeably worse. Also I might have to try the techron thing because my uncle swears by it but I didn't believe him until you recommended it.
That Coke bottle should have been filled in 30 seconds. Personally I don't check static flow. I check for fuel pressure under load by driving the car with the pressure gauge taped to the outside of the windshield.
Well I could be wrong but I am not blown away by that flow test, IMO it should fill the bottle real fast at no pressure like that. I think a stock turbo pump will do 2 liters in 1 minute (free flowing). My experience is that free flowing like this it'll run more than the rating, like if it's rated for 90lph or 1.5 liters per minute it'd run 2 liters per minute free flowing and 1.5 at 2.5BAR.
As for the mis-steps we did not have much info and who knows why it sat? Maybe it sat because someone did a bad timing belt job. Maybe it has bent valves and someone slapped a belt on it anyway. Miswiring may indeed be too much of a long shot but it only takes a minute to check, it's possible to miswire a V8 and just feel down on power but maybe not a 4 banger. Obviously a new mystery "ran when parked" (or so they'd have you believe) car should have all the basics checked.
That Coke bottle should have been filled in 30 seconds. Personally I don't check static flow. I check for fuel pressure under load by driving the car with the pressure gauge taped to the outside of the windshield.
I agree on both points but I hesitate to suggest checking fuel pressure while driving due to the significant potential for leak and fire. It's so easy to catch a 944 on fire with a fuel leak right by those old plug wires and cap. The DME relay jumper is much safer and you get some data. Having done the free flow test you can tee in the pressure gauge and pinch the hose until you get good pressure and repeat the test if you want. I suggest testing below the FPR threshold to keep it from returning fuel, or such that it shouldn't be returning.
That is a valid point. However I do make certain that the connections are secure and that's theres no chance of leaks.
That's actually a pretty good idea, but I think the flow test alone shows somethings wrong. By the way thanks for linking that Clark's garage page, I wasn't even aware Clark's garage had a procedure on a flow test.
So for me the next thing I'm going to check is the wiring to the fuel pump. Maybe it's not getting full voltage.
If the fuel supply is not up to par it could be a bad FPR or a clogged sock filter in the tank as well. If you get more (free, 0 psi) flow with the return line clamped off then you know the FPR is not doing it's thing.
01-11-2018, 03:42 PM
